The present invention generally relates to test contactors used to establish an electrical interface between an integrated circuit (IC) device under test and a circuit board, and, more particularly, relates to contactor nests used to guide an IC device into contact with an array of contact pins of an interposer that electrically interfaces with a circuit board.
Contactors are widely used to hold IC devices onto a test or load board for test or burn-in. Such contactors typically include an interposer and contactor nest. The interposer, which contains an array of conductors that match up with the I/O contact pads on the device under test (DUT), provides an electrical interface between the DUT and the test board. The contactor nest guides the DUT onto the interposer. The interposer can be integral part of the contactor or a separate part.
Contactor nests have pockets into which DUTs are typically inserted and removed by automated handling equipment. Typically, the top openings of these pockets have relatively short and sharply angled lead-in walls followed by a relatively long straight-walled guide section that conforms in size and shape to the DUT package for which the contactor is designed. The angled lead-in walls serve to center the IC package in the pocket of the contactor nest as it feeds the DUT into the pocket's straight-walled guide section; the straight-wall section guides the centered IC package the rest of the way through the pocket onto the interposer. However, the difficulty with such contactor nest designs is that DUTs frequently jam as they are passed through the straight-walled guide section of the contactor nest pocket due to the tight tolerance involved and mismatches caused by out-of-tolerance DUTs and thermal expansion. Jamming leads to frequent “drop-outs” of DUTs during high volume testing.
Another problem encountered with existing contactor nest designs has to do with the electrical contact between the IO contact pads on the DUT packages and the electrical interface pins of the interposer of the contactor. The long straight-walled guide portion of the contactor nest acts to guide the centered IC package against the contactor's pin array in a direction that is perfectly perpendicular to the spring pins of the interposer's pin array. Any foreign material that may exist on the contact pads of the DUT is compressed between the DUT's contact pads and the opposing interposer spring pins. If the spring loaded plunger ends of the interposer pins do not exert enough force to break through this foreign material, degradation in the electrical contact will result.
The present invention overcomes the drawbacks of existing contactors by providing an improved contactor nest that significantly reduces the potential for jamming of the chip in the contactor nest, and consequently reduces the frequency of dropouts that occur with automated chip testing equipment. The present invention further provides an improved contactor for an IC device that mitigates the deleterious effects that foreign material on the DUT contact pads have on the conductivity between the pads and the transposer pin array.